A glass forming machine comprises individual sections each having a plurality of mechanisms for performing various glass forming functions. Several of the mechanisms are actuated by air cylinders which cause the mechanism to move rapidly from one position to another. Although it is desirable to operate the mechanisms at production speeds, the fragility of the glassware itself presents a limitation on the maximum speed obtainable. In order that such air cylinders can accomplish a glass forming function at production speeds without destroying the glassware, the piston of the cylinder is cushioned at the end of its stroke against the base of the cylinder. Since the air between the piston and the base of the cylinder is compressed as the piston strokes toward the base, cushioning is conveniently accomplished by controlling the rate at which the air is exhausted therefrom.
In the past, cushioning was accomplished by using a side port through the wall of the cylinder in conjunction with a port in the base of the cylinder. Before reaching the side port, the piston moves in operation at a production speed because the air in the cylinder is being exhausted at a high rate through both the side port and the base port. When the piston approaches the end of its stroke and closes off the side port, it slows down since the air is being exhausted at a lower rate through the base port only. Further cushioning was accomplished by using a variable aperture needle valve in conjunction with the base port as disclosed in U.S. Pat. No. 4,007,028 granted Feb. 8, 1977 to A. T. Bublitz, et al. The patent discloses apparatus comprising a needle valve having a worm wheel connected to the free end of the valve stem and opposing worm gears driven by a remote motor for alternately engaging the worm wheel to open or close the valve. Additional cushioning was accomplished by using a cushion plug affixed to the piston and a cushion socket formed in the base of the cylinder for receiving the cushion plug. When the piston approaches the end of its stroke, the plug is forced into the socket which compresses the air therein to further reduce the speed of the piston before impact against the base.